Papillary thyroid carcinoma (PTC) is the most frequent form of thyroid cancer, and the association with primary hyperparathyroidism have been well described. Although, a synchronous PTC and renal hyperparathyroidism (HPT) is a rare event, with pathogenetic interest ,often detected only by surgery. We suggest that the association between thyroid carcinomas and renal hyperparathyroidism should be always considered, highlighting several factors that may favour malignant transformation.